Abstract
The p-type Si layer in a-Si and μc-Si solar cells on foil needs to fulfil several important requirements. The layer is necessary to create the electric field that separates the photo-generated charge carriers; the doping also increases the conductivity to conduct the photocurrent to the front contact; on the other hand, the p-layer should transmit the incident light efficiently to the intrinsic absorber layer. We show that it is possible to study TEM samples prepared, for analysis of possible layer defects, by focussed ion beam milling to detect boron and carbon concentrations as low as 1020cm-3, using core-loss EELS combined with numerical analysis. We control the band gap and activation energy of p-a-SiC by varying the B2H6 and CH4 flow during deposition in the process chamber. We have found a linear relation between the activation energy of the dark conductivity Eact and the optical band gap E04. Modelling shows that the optimum efficiency in nip solar cells is obtained when the p-a-SiC band gap is slightly larger than the band gap of the absorber layer. We have assessed the potential of core-loss EELS for detecting B and C concentrations as low as 1020cm-3 in a spatially resolved manner, and of low-loss EELS as a probe of the local variations in plasmon energy.
Original language | English |
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Journal | Journal of Non-Crystalline Solids |
Volume | 358 |
Issue number | 17 |
Pages (from-to) | 2179-2182 |
ISSN | 0022-3093 |
DOIs | |
Publication status | Published - 2012 |
Event | 24th International Conference on Amorphous and Nanocrystalline Semiconductors (ICANS 2011) - Nara, Japan Duration: 21 Aug 2011 → 26 Aug 2011 |
Conference
Conference | 24th International Conference on Amorphous and Nanocrystalline Semiconductors (ICANS 2011) |
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Country/Territory | Japan |
City | Nara |
Period | 21/08/2011 → 26/08/2011 |
Keywords
- Electron energy loss spectroscopy (EELS)
- Thin film Si
- Transmission electron microscopy
- p-Type SiC
- Doping concentration